This invention relates to a signal recording device for transmitting recording data signals via a rotary transformer to a rotary drum having a rotary head for recording data.
In a video tape recorder (VTR) in which a recording medium such as a magnetic tape is used and data is recorded thereon by a rotary head provided on the rotary drum, recording signals are exchanged by a rotary transformer connected between a rotor side, that is a rotor drum side, and a stator side, that is a stator side.
FIG. 1 shows a schematic arrangement of an analog VTR. Referring to FIG. 1, the analog VTR has a simplified construction in which a recording head 40 has its winding directly connected to a winding of a rotary transformer 38, while a playback head 41 has its winding directly connected to a winding of a rotary transformer 39, and a recording amplifier 34 and a playback amplifier 35 are arranged on the stator side.
For data recording, picture signals entering a signal input terminal 30 are sent to a modulator 32 for modulation. At this time, a signal switching unit 36 is set to a terminal a, while a signal switching unit 37 is set to a terminal c. Thus, output signals of the modulator 32 are recorded via the recording amplifier 34, signal switching units 36, 37 and the rotary transformer 38 as recording signals from the recording head 40 on the magnetic tape, not shown. For data reproduction, recorded signals are read out by the playback head 41 from the magnetic tape, not shown, so as to be outputted as playback signals. At this time, the signal switching unit 36 is set to a terminal b, while the signal switching unit 37 is set to a terminal d. Thus the playback signals from the playback head 41 are routed via the rotary transformer 39, signal switching units 37, 36 and the playback amplifier 35 to the demodulator 33. The demodulator 33 demodulates the playback signals sent thereto into picture signals which are outputted at a signal output terminal 31.
With the rotary transformer of the above-described analog VTR, playback signals which are weaker in signal level than the recording signals are erased by cross-talk such that the so-called recording confidence function of carrying out reproduction simultaneously with recording cannot be realized. With a digital VTR, since the signals handled are of a higher frequency, stray capacitance or inductance produced by interconnection or the rotary transformer deteriorates high-range characteristics. In addition, the number of stages of the rotary transformer is increased due to concurrent recording of plural channels, thus posing a problem.
For overcoming this inconvenience, the system of loading a recording/playback amplifier on a rotary drum has become predominant in particular in a digital VTR. With such signal recording/reproducing apparatus, since the recording/playback signals transmitted through the rotary transformer can be matched in signal level, it becomes possible to alleviate the effects of crosstalk on the recording/playback signals. On the other hand, since the distance between the head and the amplifier can be reduced significantly, the adverse effects of the interconnection may also be lessened. In addition, since a switching circuit can be loaded on the rotary drum, the two opposing heads can exploit one stage of the rotary transformer in common.
However, with the above-described digital VTR, switching, mode exchange or adjustment of the recording current is taken charge of by the rotary drum. For effecting these control operations from the stator, it becomes necessary to transmit control signals to the rotary drum. In general, serial data signals are used because of limitations in routes.
FIG. 2 shows a data format for a compound serial control signal having a waveform of a conventional parallel-serial conversion system. This signal is referred to herein as an MPX signal. A 16-bit bit pattern BP in the MPX signal controls 16 lines: from line 0 to line 5. For turning e.g., the fifth control line on, the MPX signal in which the fifth bit of the bit pattern BP is set to 1 is transmitted.
The MPX signal, as the serial data signal, is generated by latching the information of each control line on the stator side, changing the latched value responsive to the operating mode or the timing and converting the changed value by parallel/serial conversion by a shift register. These serial data signals are inputted to the rotary transformer. On the rotary drum side, the serial data signals are converted by serial/parallel conversion for generating the information which is the same as the latched information on the stator side. The circuitry for generating and converting the MPX signal is of a simplified construction.
Meanwhile, with the MPX signal, generated as described above, since a timing signal having a pre-set time width is allocated to each control line, the length of the serial data is increased with increase in the number of the control lines. Thus, when the transmission of the serial data signal is started, transmission of the next serial data signal cannot be started until the termination of transmission, so that the time interval from a given change to the next change is increased.
On the other hand, since the control line is specified by a timing, it is impossible to shorten the time by employing a method of partially transmitting a portion of serial data.
In addition, if the number of control lines is increased, more timings are required, so that control that is needed becomes frequently difficult. That is, since the resolution along time axis becomes shorter, sufficient control cannot be achieved despite increase in the number of control lines.